In a fuel cell in which electrode catalyst layers being completed by laminating supports with catalysts loaded are adhered to a solid polymer-electrolyte membrane that has selective permeability to hydrogen ion; and in which the solid polymer-electrolyte membrane and the electrode catalyst layers are held by a pair of gas diffusible electrodes while interposing them therebetween, electrode reactions, which are expressed by reaction equations being specified below, develop at both electrodes (anode and cathode), which hold the solid polymer-electrolyte membrane between them, depending on their polarities, thereby obtaining electric energy.Anode (Hydrogen Electrode): H2→2H++2e−  (1)Cathode (Oxygen Electrode): 2H++2e−+(½)O2→H2O  (2)
Humidified hydrogen or a fuel gas including hydrogen passes through the anode gas diffusion layer being an electricity collector as well, and then arrives at the catalytic layer, and thereby the reaction of equation (1) occurs. The hydrogen ions H+ that are generated at the anode by means of the reaction of equation (1) permeate (diffuse through) the solid polymer-electrolyte membrane, and then move toward the cathode being accompanied by water molecules. Simultaneously therewith, the electrons e- that are generated at the anode pass through the catalytic layer and gas diffusion layer (electricity collector), then pass through a load that is connected between the anode and the cathode by way of an external circuit, and eventually move to the cathode.
On the contrary, at the cathode, an oxidizing-agent gas including humidified oxygen passes through the cathode gas diffusion layer being an electricity collector as well, reaches the catalytic layer, and then receives electrons that have flowed from the external circuit through the gas diffusion layer (electricity collector) and catalytic layer so that it is reduced by the reaction of equation (2), and eventually combines with the protons H+ that have flowed from the anode through the electrolyte membrane to turn into water. A part of the generated water comes into the electrolyte membrane by means of concentration gradient, diffuses toward the fuel electrode to move thereto, and another part thereof evaporates, then diffuses to a gas passage through the catalytic layer and gas diffusion layer, and is eventually discharged together with the unreacted oxidizing-agent gas.
Thus, at both of the anode side and cathode side, the condensation resulting from water occurs to cause the flooding phenomenon, and thereby there is a problematic point in that the electric-power generation performance might be impaired.
On the other hand, for the downsizing of fuel-cell system, making it produce a high output in high current-density load region is necessary and indispensable. In Patent Literature No. 1 and the like being mentioned below, investigations on the performance in high current-density load region were carried out by means of binary system or ternary system alloy catalysts of platinum with transition metal elements.
Moreover, as a catalyst for fuel cell, various platinum-cobalt system catalysts have been studied by UTC Fuel Cells Corporation, and their presentations have been made at academic conferences. According to those, it is said that, in platinum-cobalt binary catalysts, the cell voltages are higher than those in the other platinum-cobalt system catalysts; especially, this tendency is said to be strong in high current-density load region.
Patent Literature No. 1: Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-24,798;
Patent Literature No. 2: Japanese Patent Gazet to No. 2, 928, 586;
Patent Literature No. 3: Japanese Patent Gazette No. 3,353518; and
Patent Literature No. 4: Japanese Unexamined Publication (KOKAI) Gazette No. 10-162,839